1. Field of the Invention
The present invention relates to a motion compensation device and method which compensates for hand tremor motions and other sources of image blurring motion and vibration in a camera and related optical systems.
2. Description of the Related Art
Optical systems project an image onto an image plane. Conventional image blur suppression device suppress, or reduce, blurring of the image. A motion compensation device is a type of image blur suppression device, and compensates for motion incident upon the optical system. Motion is typically imparted to the optical system by vibrations in the optical system, or in a surrounding holding member. In general, conventional motion compensation devices cause a compensation lens to shift counter to the motion of the optical system so as to shift the image projected by the optical system relative to the optical system. Conventional cameras use a motion compensation device to suppress image blur resulting from motion of the camera. Such motion is typically caused by hand tremors of the photographer.
A motion compensation device in the prior art has a structure as disclosed in Japanese Laid-Open Patent Publication JP-6-67274. In JP-6-67274, a motion compensation device is disclosed which is equipped with a blurring motion compensation lens, and a blurring motion compensation lens frame which supports the blurring motion compensation lens. A blurring motion compensation lens drive mechanism is used to drive this blurring motion compensation lens frame. A convex locking member fits into a concave surface formed in this blurring motion compensation lens frame and locks the blurring motion compensation lens frame. Driving the locking member is a locking member drive mechanism which engages or releases the locking member and the concave surface. This locking member drive mechanism is equipped with a slide which moves rectilinearly, a permanent magnet, a solenoid coil and an assembled plunger-type latch solenoid. This plunger-type latch solenoid, when properly electrified, cancels the magnetic field of the permanent magnet and operates to release the locking member from the concave surface. The plunger-type latch solenoid, when properly electrified, also can increase the magnetic force of the permanent magnet and operates to engage the locking member and the concave surface.
In the motion compensation device of Japanese Laid-Open Patent Publication JP-6-67274, when a discrimination unit determines that the blurring motion compensation lens is not locked, the blurring motion compensation lens frame is locked by an electrical locking device. When a defect occurs in the locking member drive mechanism, the electrical locking device locks the blurring motion compensation lens frame so that the optical axis of the whole photographic optical system and the optical axis of the blurring motion compensation lens coincide. In such a situation, it is possible to perform normal photography. Also using this method, damage to the blurring motion compensation lens due to vibration and failure of the blurring motion compensation lens drive mechanism are prevented.
The prior art motion compensation device, however, makes it necessary to engage or release the locking member from the concave surface by the electrically conducting state of the plunger-type solenoid. Moreover, the prior art motion compensation device makes it necessary to lock the blurring motion compensation lens frame by the electrical locking device when the blurring motion compensation lens frame could not be locked by a locking member drive mechanism. Accordingly, the prior art motion compensation device necessitates an electric power source in order to drive the locking member drive mechanism and to drive the electrical locking device. Generally, in a camera system comprising a lens body and a camera body in which the lens body is interchangeable, a motion compensation device on the lens barrel itself has a power supply disposed in the camera body. Since the power supply, normally a battery, is not contained in the lens barrel where the blurring motion compensation lens frame is located, when the power supply battery of the camera body is removed or the lens barrel is removed from the camera body, the problem arises of not being able to lock the blurring motion compensation lens frame using the locking member drive mechanism or the electrical locking mechanism.